Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$118.69	7.193%	$127.2274	$127.23	$127.25	$127.20
Purchase #2	$210.53	12.515%	$236.8778	$236.88	$236.90	$236.90
Purchase #3	$163.94	6.210%	$174.1207	$174.12	$174.10	$174.10
Purchase #4	$58.75	11.588%	$65.558	$65.56	$65.55	$65.60
Purchase #5	$235.92	12.522%	$265.4619	$265.46	$265.45	$265.50
Purchase #6	$105.61	5.147%	$111.0457	$111.05	$111.05	$111.00
Purchase #7	$11.78	3.626%	$12.2071	$12.21	$12.20	$12.20
7 purchase totals =	$905.22		$992.4986	$992.51	$992.50	$992.50